Hi all

I own a 2007 Redline 925 and wanted to ask anyone one here if they happen to know where I could go to find the specifications regarding the size of the headtube because I want to swap out my current fork for another. I've measured the diameter on the fork and it measures 1" but it seems to have quite some space when I slip it into the frame which makes me think that it might actually need a 1 1/8" fork. I'm not sure if all forks are supposed to have room or if they're supposed to take up all the room inside. I also assume that because the stem uses a shim to fit on the steerer because its 1 1/8". I bought the bike used so I'm unfamiliar with the components on it and have not been able to find these specifications.

Thank you all